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Thread: Difference in Wire Rope

  1. #1
    Associate Engineer
    Join Date
    Jul 2015

    Difference in Wire Rope

    Dear all, I'm new to wire ropes, and recently I'm facing a problem .

    A crane that originally uses 6x Fi(29) Wire rope needs a wire rope replacement. A vendor quoted my company for a 6x36 instead.

    As far as I understand, 29 and 36 is the number of wire strands in the wire rope surrounding the core. I've also looked into the tensile strength and load per unit length and it's the same. Does this mean that these two ropes are interchangable? Is there any other difference that I should know about?

    Thanks in advance for any answer.

    *p.s. I'm also new to the work force, so any help is appreciated.*

  2. #2
    Lead Engineer RWOLFEJR's Avatar
    Join Date
    Mar 2011
    Rochester Pennsylvania
    The 6 x 36 will be a little more flexible.
    Advice... Don't go cheap on this. Make certain that the cable is intended and certified for use on a crane of your lifting capacity. Get the cert's with the cable and put it in your file on the crane.


  3. #3
    Associate Engineer
    Join Date
    Jul 2015
    I received a reply from a supplier, apparently 29 is more abrasion resistant than 36, whereas the 36 is more fatigue resistant. 36 is also more flexible as you said.

    I understand that I can't go cheap with this, I'm just worried that the 36 might not suit the crane design since it was originally meant for 29 usage. Some suppliers said that it wouldn't be an issue, but i'm always looking for a third or fourth opinion.

    Thanks Bob

  4. #4
    Project Engineer
    Join Date
    Feb 2011
    Spokane, WA

    Because you are posting here, seeking this kind of knowledge,
    I suspect you are dealing with the main hoist line on a simple
    boom truck.

    In that case, you will want to go with the design spec: 6x29.
    No sense in taking on the liability of changing from the spec.

    Btw, 6 x 29 is six strands consisting of 29 wires each.
    The 6 strands surround a central core.

    If my assumption is correct, in your application,
    you will be more concerned about wear than flexability.

    Although I deal with wire rope on a nearly daily basis,
    and am a nationally certified rigger,
    I do not claim, infer, state, declare or imply that this
    advice is applicable in any way to your specific question,
    environment or situation.

    Last edited by dalecyr; 08-02-2015 at 10:58 AM.

  5. #5
    You know it, wire ropes are winded left or right in manufacturing. Why is it important in use?

  6. #6
    Principle Engineer Cragyon's Avatar
    Join Date
    Feb 2013
    Newark, NJ
    Winding left or right is irrelevant to function, the winding is to keep the rope or cable together when not under load. Whena load is placed on a rope, torque iscreated within the rope as wires andstrands try to straighten out. This isnormal and the rope is designed tooperate with this load-induced torque.However, this torque can cause loadsto rotate. Load-induced torque can bereduced by specially designed rotationresistant ropes.

    Thetorque produced by the outer strands of the rope is in the same directionand add together. In rotation resistantropes, the lay of the outer strands is inthe opposite direction to the lay of theinner strands, thus the torques producedare in opposite directions and the torquessubtract from each other.

    Moreover, under load there is a compression effect on the inner stands which can increase the load carrying capability of the rope

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